Data bases for stroke and traumatic coma provide observational data that require both critical application of existing statistical methodology and development of new statistical techniques, in order to extract meaningful information and to draw valid conclusions from the accumulated data. Methodology has been developed to ensure validity and quality control of the collected data. Methods for data analysis which take account of variation due to observers, centers, and patient cohort characteristics are being developed. An invited paper concerning the use of medical data bases for clinical research was presented at the Annual Eastern Regional Biometrics Society Meeting in April 1979.